These studies are directed toward detailed investigation of the control of intestinal ion secretion with emphasis on the mechanism by which several agents may induce secretion. In addition, studies have been directed toward evaluation of possible agents which will inhibit fluid and electrolyte secretion. During the past year completed studies included the demonstration that bile salts induce ion secretion in the colon by increasing mucosal cyclic AMP. Further, detaled evaluation of the effect of shigella enterotoxin on fluid and electrolyte secretion in the rabbi ileum suggested that this secretion may be mediated by a non-cyclic AMP process. Other studies evaluated the colonic effect of bacterial enterotoxins and indicted that cholera enterotoxin altered fluid movement in the colon but that E. coli and shigella enterotoxins did not. Finally, studies of the mechanism of increased oxalate absorption which is observed in ileal dysfunction suggested that bile salts may increase oxalate absorption by producing a non-specific alteration of mucosal permeability. BIBLIOGRAPHIC REFERENCES: Binder, H.J., Filburn, C and Volpe, B.: Bile Salt Alteration of Colonic Electrolyte Transport: Role of Cyclic Adenosine Monophosphate. Gastroenterology 68:503-508, 1975. Binder, H.J., Filburn, B. and Floch, M.: Bile Acid Inhibition of Intestinal Anaerobic Organisms. Amer. J. Clin. Nutr. 28:119-125, 1975.